Pinch rollers forcibly contacted to capstan shafts during tape feeding must be detached therefrom upon interruption of the power supply so as to avoid their deformation or shortening of life.
The prior art method of this detachment is to couple pinch rollers to a head plate with a head thereon, so that the head plate which retracts upon power supply interruption conveys the capstans. This method, however, requires a complicated construction, because the head plate must be carried back to the advanced position, which requires a mechanism to move the head plate back and forth responsively to removal and supply of the power to the system. Considering that the head plate must be moved back and forth to place the tape player in the fast-forwarding or rewinding mode or upon loading or ejection of a tape, the construction to also move it back and forth upon interruption and supply of the source power invites a complicated arrangement of a control means.
A tape player in general includes a channel changing mechanism to change the tape feeding direction from forward to reverse or vice versa.
The channel changing mechanism is configured to alternatively compress or detach right and left pinch rollers with respect to capstan shafts by displacement of a pinch roller change plate which is operatively linked to a driving device driven by a motor. The pinch roller change plate has forward- and reverse-mode cams which engage the right and left pinch rollers, respectively. The cams are configured to compress one of the pinch rollers to the associated capstan and detach the other pinch roller from the other capstan when the pinch roller change plate is locked at its rightmost or leftmost position.
The present inventor proposed a mechanism to detach the pinch rollers from the capstan shafts, without moving the head plate, in order to eliminate the above-described drawbacks caused by frequent displacements of the head plate. More specifically, the inventor's proposal was to use a resilient member such as a spring to bring back the pinch roller change plate to its neutral position where the both pinch rollers stand apart from the capstan shafts, when the power supply is interrupted. Thus, the head plate need not displace upon interruption of the power supply. This significantly simplified the construction and the control means, and also contributed to a further reduction of the overall size of the tape player.
However, if the channel changing mechanism is configured so that the pinch roller change plate is moved by a power plate which is in turn moved by rotation of a power gear driven by a motor, the inventor's proposal still involves the following problem.
In such a channel changing mechanism, the power gear has two, forward- and reverse-mode chipped portions along the geared circumference, so that, during a play mode, the power gear is locked at an angular position where one of the chipped portions faces a drive means and the power gear is detached from the motor so as not to change the channels of the tape. A change of the channels is effected by a reciprocation of the power plate when the power gear is unlocked, is rotated by a half revolution by the motor power, and is locked again at an angular position where the other chipped portion faces the drive means. When the pinch roller change plate is returned to its neutral position by the spring force upon interruption of the power supply, the power plate operatively linked thereto also returns to its neutral position. Concurrently, the power gear is going to rotate together. However, to allow the power gear to rotate, it is necessary to unlock it and forcibly rotate the motor which is in response in engagement with the motor-driven gear, thereby applying a load to the motor and relevant mechanisms. The load, in turn, becomes a resistance against movements of the power plate and the pinch roller change plate. Therefore, the spring force to return them to their neutral positions must be significantly large, and the driving force to move the plates against the large resilient force must be also large, accordingly.
The channel changing mechanism moves the pinch roller change plate from the forward- to reverse-mode position or vice versa, as explained above. If the power plate returns to its neutral position when the power supply is removed as described above, the pinch roller change plate cannot return to its preceding position unless the power plate is returned to its former position by the power gear. However, since the power gear is locked every half revolution to lock the power plate at the forward- or reverse-mode position in the prior art mechanism, it is inevitable that when the power is supplied, the power gear is locked after a half revolution and locks the power plate at a position opposite to that before the preceding interruption. This means that the channel is changed from one to the other every time when the power switch is turned on. Therefore, a user is compelled to make an additional channel changing operation after a power-in to the player, in order to feed the tape in the same direction as that before the preceding power-off of the player.
Besides this, in a tape player in general, a tape in position is liable to produce a slack when the tape player is first activated after the tape is loaded in position or the tape player is activated again after the power supply is once cut off or when the tape player is placed in the tape playing mode from the fast-forwarding or rewinding mode. If the tape is driven as it is, the slack is often eated between the pinch roller and the capstan and accumulates thereon, thereby causing a sudden interruption of the tape player or a serious damage to the tape. In this connection, many tape players are configured to remove such a tape slack by rotating a take-up reel base in a slight time after the take up reel base begins to rotate due to engagement with the idler gear and before the pinch roller is compressed to the capstan shaft.
The prior art tape slack removing mechanism described above, however, involves the following drawbacks.
In a slight time for removal of the tape slack, it is only the take-up reel base that rotates due to engagement with the idler gear. Therefore, as the result of the tape slack removal, a so-called tape run, wherein the tape is feeded ahead, occurs. Such a tape run is infavourable because the player fails to play a significant part of the tape when the tape slack is large and because an abnormal sound is produced due to a high velocity.
A proposal to overcome this problem is to employ a lock mechanism which locks the take-up reel base by friction produced between the reel base and an elastic member encircling the circumference of the reel base. However, provision of such a mechanism unique to the locking of the reel base makes the tape player construction extremely complicated and large-scaled.